gh-1084: Add config to run on archer2 with GPU

[connoraird]

Description

• Adds submission scripts and documentation of how to run the regression tests on Archer2 with GPU.

Refs: #1084

Checks

• Is your code passing linting?
• Is your code passing tests?
• Have you added additional tests (if required)?
• Have you modified/extended the documentation (if required)?
• Have you added a one-liner changelog entry above (if required)?